#include <EditConstants.au3>
#include <GUIConstantsEx.au3>
#include <WindowsConstants.au3>

GUICreate("My GUI edit",500,500)
Local $idMyedit = GUICtrlCreateEdit("",0,0, 500, 250, $ES_AUTOVSCROLL + $WS_VSCROLL)

Local $sym =   GUICtrlCreateLabel("Количество введенных символов 0",0, 300,500,250)

GUIRegisterMsg($WM_COMMAND, "_WM_COMMAND")

GUISetState(@SW_SHOW)

While 1
Switch GUIGetMsg()
Case $GUI_EVENT_CLOSE
ExitLoop
EndSwitch
WEnd

Func _WM_COMMAND($hWnd, $Msg, $wParam, $lParam)
#forceref $hWnd, $Msg, $lParam
Local $cId
$cId = BitAND($wParam, 0xFFFF)
Switch BitShift($wParam, 16)
Case  0x300  ; $EN_CHANGE
$text = GUICtrlRead($idMyedit)
GUICtrlSetData($sym ,"Количество введенных символов " & StringLen($text))

EndSwitch
EndFunc